Amir Khan "should retire now" after being pulled out of his fight with Terence Crawford, says Steve Bunce.
Briton Khan, 32, took a low blow from American WBO world welterweight champion Crawford in the sixth round at Madison Square Garden in New York.
Unbeaten Crawford, 31, later accused Khan of quitting which the former two-weight world champion denied.
"We can't keep applauding him for his heart and guts and bravery," BBC pundit Bunce told the 5 Live Boxing podcast.
"He'll be throwing punches until the cows come home."
Khan was knocked down in the first round by Crawford and was behind on all three judges' scorecards when the fight ended.
Crawford - who has held world titles in three weight divisions - drove a left hook into Khan's groin 47 seconds into the sixth, leaving him in "too much" pain to continue.
"I thought Amir Khan looked awkward, his balance looked poor, his shot selection wasn't great," Bunce added.
"Sometimes his feet can be bad when he's lazy. That's not a criticism, that's a fact.
"We're looking at a kid who should retire now. I'm looking at the end of the fight, being outclassed even though you're fighting your heart out, how poor his feet were, how desperately he missed sometimes."
'He wasn't looking for a way out' - did Khan quit?
Khan's trainer Virgil Hunter said the boxer was "incapacitated" by Crawford's low punch, with Khan adding he "couldn't think straight" after the blow.
On Sunday, Khan once again rejected Crawford's claims that he had quit, saying on Twitter "I'd rather get knocked out cold" - before revealing he was "peeing blood".
"I don't think there is any suggestion he got hit with a half shot and decided to quit," said Bunce.
"Crawford doesn't think he hit him low, so of course Crawford thinks he quit because he thinks he hit him with a legitimate shot.
"I've looked at it in some detail and it definitely comes from the leg and looks like it goes into the groin protector. Can that catch you at such an angle? Yes it can."
Khan has faced criticism throughout his career, both in and out of the ring, and Bunce believes Saturday's finish could add fuel to the fire.
"It's going to run and run, because it will suit some people's agenda to add 'quitter' to 'glass chin', to add 'quitter' to 'flash so-and-so'," Bunce added.
"I can't say with certainty that he quit. I can't say with certainty that at that point he was hurt enough.
"But I know for one thing that he wasn't looking for a way out."
Former world champion Barry McGuigan said it was "very dangerous" to call Khan a quitter.
Speaking on BBC Radio 5 Live's Sportsweek programme, McGuigan said: "You look at Khan's career and the fights he's been in and the one thing he always had was immense courage, determination and getting up off the floor.
"You think of the Breidis Prescott fight, the Canelo (Alvarez) fight, the Danny Garcia fight - there's no quit in him.
"I just think he took the intelligent option and got out because he was down.
"If he'd gone on and been humiliatingly knocked out and dropped several times and then flattened, then people would have been calling for him to stop.
"Now I suppose with Virgil Hunter's decision, he's got the chance of resurrecting the possibility of a fight with Kell Brook somewhere down the line."